mcp-tool-server
A custom MCP server with 6 utility tools (file search, file reading, math calculation, JSON formatting, time query, system info) that demonstrates MCP protocol workflow and integrates with LangChain agents.
README
自定义 MCP Server — 从零理解 MCP 协议
这是什么？
一个从头手写的 MCP (Model Context Protocol) 工具服务器，包含 6 个实用工具。
配合 LangChain Agent 客户端，完整演示了 MCP 协议的核心工作流：
MCP Server (工具提供方) LangChain Agent (工具消费方)
───────────────────────── ───────────────────────────
定义工具 + 参数 Schema ←→ 自动发现工具 (tools/list)
等待工具调用 ←→ 调用工具 (tools/call)
返回执行结果 ←→ LLM 推理 → 最终回答
项目结构
my-mcp-server/
├── mcp_server.py # MCP Server: 6 个工具, 支持 HTTP/stdio 双模式
├── agent_client.py # LangChain Agent: 自动发现并调用 MCP 工具
├── pyproject.toml # 依赖清单
├── .env.example # 环境变量模板
└── README.md # 你正在看的文件
快速开始
1. 安装依赖
pip install fastmcp langchain langchain-openai langchain-mcp-adapters python-dotenv
2. 设置 API Key
cp .env.example .env
# 编辑 .env, 填入你的 OPENAI_API_KEY
3. 启动 MCP Server
# 终端 1: HTTP 模式 (推荐，方便调试)
python mcp_server.py --transport http --port 8000
4. 运行 Agent 客户端
# 终端 2: 交互模式
python agent_client.py
# 或者单次提问
python agent_client.py "帮我搜索当前目录下所有的 Python 文件"
包含的工具
| 工具名 | 功能 | 示例 |
|---|---|---|
search_files |
按文件名模式搜索本地文件 | "找所有 .py 文件" |
read_text_file |
读取文本文件内容 | "读取 README.md" |
calculate |
安全的数学表达式求值 | "计算 3+5*7" |
json_formatter |
JSON 格式化/美化 | "格式化这段 JSON" |
get_current_time |
查询当前时间 (支持时区) | "现在几点了?" |
system_info |
查看系统信息 | "我的系统是什么?" |
MCP 协议核心概念
tools/list — 工具发现
Agent 启动时调用，服务器返回所有可用工具的清单。每个工具包含：
- name: 工具名 (如
calculate) - description: 功能描述 (LLM 读这个来决定要不要用)
- inputSchema: 参数定义 (JSON Schema 格式，描述每个参数的类型、是否必填)
tools/call — 工具调用
Agent 决定使用某个工具时调用，传入工具名和参数。服务器执行后返回结果。
为什么不用硬编码？
传统做法:
# 每加一个工具都要改 Agent 代码
tools = [calculator_tool, search_tool, ...] # 硬编码
MCP 做法:
# Agent 启动时自动发现工具，不用改代码
mcp_client = MultiServerMCPClient({"server": {"url": "..."}})
tools = await mcp_client.get_tools() # 自动发现!
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